Cross flow tunnel freezer system

ABSTRACT

A system processes a food product with a cooling gas and includes a housing with a chamber; a blower in communication with the chamber for circulating the cooling gas; a baffle disposed in the chamber for dividing the chamber into a first region for exposing the food product to the cooling gas and a second region in which the cooling gas is moved by the blower for recirculation to the first region of the chamber; an arcuate member disposed in the chamber in spaced relationship with the baffle for providing a flow path between the first and second regions, the arcuate member coacting with the baffle to guide the cooling gas into the flow path; and conveyor means disposed for movement through at least one of the first and second regions for supporting and delivering the food product through the cooling gas.

BACKGROUND OF THE INVENTION

Conventional tunnel freezers utilize axial flow fans mounted above the product to generate gas flow which impinges the surface of the product and promotes heat transfer. Local velocities from these fans are high, in the range of 2000 feet per minute (fpm). However, there are significant gaps between fans and therefore, large areas are not covered with a uniform high velocity flow. As a result, the total heat transfer coefficient for these processes is low. In addition, these freezers require sufficient height to allow gas to enter from above the axial fan, then be pressurized and distributed onto the product perpendicular to the surface of the product.

Impingement heat transfer is a means of applying airflow for freezing which is very effective at achieving high heat transfer coefficients. With impingement freezing, nearly 85% of the total freezer area can achieve high velocity airflow. However, the gas flow distribution system for impingement freezing is very complicated, as gas must be pressurized, forced through an impingement plate (having 5% open area), fed into specially designed return channels and then brought back into the fans to be recirculated. These systems are costly to build, complex, difficult to clean and to maintain the proper openings of the impingement plates during operation as they tend to clog with cryogenic freezing snow and ice. To unclog and remove the snow and ice, a plate vibration assembly must be installed, which adds cost and complexity to the system.

SUMMARY OF THE INVENTION

One embodiment of the invention provides an apparatus for processing a food product with a cooling gas, comprising a housing; a chamber disposed in the housing; a blower in communication with the chamber for circulating the cooling gas in the chamber; a baffle disposed in the chamber for dividing the chamber into a first region of the chamber for exposing the food product to the cooling gas and a second region of the chamber in which the cooling gas is moved by the blower for recirculation to the first region of the chamber; an arcuate member disposed in the chamber in spaced relationship with the baffle for providing a flow path between the first and second regions, the arcuate member coacting with the baffle to guide the cooling gas into the flow path; and conveyor means disposed for movement through at least one of the first and second regions for supporting and delivering the food product through the cooling gas.

Another embodiment of the invention provides a method of applying a cooling gas to a food product, comprising conveying a food product along a first path to be cooled in a chamber for cooling; circulating a cooling gas in the cooling chamber along a second path perpendicular to an entire length of the first path; and exposing the food product to the cooling gas moving along the second path for an entire length of the first path in the cooling chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments of the invention, reference may be had to the following drawings taking in conjunction with the description of the invention, of which:

FIG. 1 shows a schematic cross-section view of a single belt freezer embodiment of the invention.

FIG. 2 shows the embodiment of FIG. 1.

FIG. 3 shows a schematic cross-section view of a dual belt freezer embodiment of the invention.

FIG. 4 shows a schematic cross-section view of another single belt freezer embodiment of the invention.

FIG. 5 shows a schematic cross-section view of still another single belt freezer embodiment of the invention.

FIG. 6 shows a schematic cross-section view of another dual belt freezer embodiment of the invention.

DESCRIPTION OF THE INVENTION

The embodiments of FIGS. 1-6 distribute airflow across a width of the freezer tunnel so that food product therein is exposed to a high velocity, for example of 2000 feet per minute (fpm), gas flow throughout the freezing process. By applying the gas as a ‘cross flow’ across a width of the belt, i.e. transverse to the direction of the belt's movement as shown in FIGS. 1-6, all of the freezer achieves the high velocity gas flow and the overall heat transfer coefficient is significantly higher than known systems. The gas flow may be applied to cover the entire or 100% of the surface area of the belt upon which the food product is transported. Testing has shown heat transfer coefficients to be as much as 300% higher using the freezer apparatus with the airflow configuration of the present embodiments.

The gas flow assembly in the embodiments provides a significant amount of space savings above the product.

As a result, the embodiments of FIGS. 1-6 can be as much as 300% shorter in length and 300% lower in height, and still achieve comparable production rates and greater efficiencies.

The embodiments have a much smaller footprint, are compact and extremely easy to clean. It is estimated that the cross flow tunnel freezer embodiments will realize at least a 50% cost savings over a comparable production rate impingement freezing system.

Benefits of the embodiments herein of FIGS. 1-6 include:

a) Heat transfer coefficients achieved in the cross flow airflow configuration at velocities in the range of 2000 ft/min (610 m/min) are comparable to those achieved in a full scale impingement freezer. These higher heat transfer coefficients are achieved with reduced power consumption over current technologies.

b) The cross flow tunnel freezer embodiments have simplicity in construction and reduced capital equipment costs. Overall height will be minimal, compared to conventional tunnel and impingement freezers. The embodiments also provide sanitation benefits, i.e. easier to clean and to maintain the cleanliness.

c) The airflow lends itself to crust freezing applications, such as for example crusting of meat logs (see FIG. 2). One will be able to achieve an even crust over the product surface with much greater efficiency and uniformity than that of a standard tunnel freezer. The embodiments herein may be suited for front end of line (“FEOL”) use in that they crust freeze products to trap moisture in the product so that a mechanical freezer can thereafter freeze the remaining portion of the product. The present embodiments may be used with flat food products, i.e. those products with low cross-sectional profile or high surface area to weight ratios.

Referring to the FIGS., FIG. 1 shows a single belt cross flow tunnel freezer configuration. Referring also to FIGS. 2-3, a freezer apparatus embodiment of the invention is shown generally at 10 and consists of a housing 12 having a chamber 14 therein in which is disposed one or a plurality of open mesh conveyor belts 16 for transporting food products 18 to be frozen, chilled or crusted within the freezer.

An airflow baffle 20 is disposed in the chamber 14 to extend over in spaced relationship from and be in registration with an entire length of each one of the conveyor belts in the chamber 14 to provide a first region “X” for chilling the air, and a second region “Y” wherein the chilled air freezes food products as shown in the FIGS. 1-3. The baffle 20 is solid or of nonporous construction, and segregates or divides the chamber 14 into the first and second regions, X and Y. In effect, airflow or cooling gas 23 provided to the first region X has a cooling fluid such as a cryogen gas injected by spigots or nozzles 22 into the airflow 23. The nozzles 22 are disposed in the chamber 14 for charging the gas flow with cryogen. The cryogen may be supplied as a cooling or cold gas such as for example gas selected from carbon dioxide, nitrogen and combinations thereof. The airflow 23 is prevented by the solid baffle 20 from contacting the food products while the air is receiving the cryogen gas in the region X. The airflow baffle 20 serves to establish a circulation path in the chamber 14.

Thereafter, the cryogen gas airflow 23 is directed along an interior arcuate sidewall surface 24 to the second region Y for providing the cryogen airflow 23 to the food products 18. The airflow 23 contacts all surfaces of the food product 18 due to the open mesh conveyor belt 16. The cryogen airflow is exposed to an entire length of the conveyor belt(s) which extends along the chamber 14 of the housing 12. Thereafter, the cryogen airflow 23 is returned to an inlet 26 of a blower 28 and recycled for subsequent chilling by the cryogen nozzles 22 in the region X. The airflow baffle 20 may be constructed and arranged in the chamber 14 such that a proximal end of the baffle 20 is positioned at the blower 28, while a distal end of the baffle extends in the chamber 14 toward the sidewall or arcuate member 24. The airflow 23 is provided along a direction transverse or perpendicular to the direction of movement of the food product 18 on the conveyor belt 16.

The freezer apparatus 10 includes the novel arrangement of the airflow baffle 20 to segregate the freezer chamber 14 into a “cryogen charging” region X for the airflow 23, and a chilling region Y for freezing food product with the airflow 23, such that the cryogen airflow sweeps across an entire length of the belt 16 in the chamber 14 and the product 18 transverse to movement of the product disposed on the belt 16.

The airflow baffle 20 is adjustable with respect to its position in the chamber 14 to accommodate a height of the food product 18 on the conveyor belt 16, and so airflow 23 efficiency can be maximized for each of the product 18. The overall height of the housing 12 may be no greater than 508 mm (or approximately 17-20 inches), excluding a height of any exhaust stacks (not shown). Parasitic heat loads will be minimized and overall system pressure drop will be less than that of a conventional impingement freezer.

FIG. 2 shows the single belt freezer apparatus 10 for crust freezing of the food product 18 such as a meat or deli log. This apparatus provides a high velocity cross flow on a meat log for even and rapid freezing around the circumference of the log. Dwell times in the range of one (1) minute are achieved. Product logs loaded across the width of the belt result in an extremely high capacity log crusting system. Overall cryogen efficiency is much greater than a conventional tunnel as a result of the cross flow circulation.

The housing 12 may be used as a “module”, whereby a plurality of the modules may be removably attached to each other to provide a crust freezing line.

Other exemplary embodiments of a freezer constructed in accordance with the invention are illustrated in FIGS. 3, 4, 5 and 6, respectively. Elements illustrated in FIGS. 3-6 which correspond to the elements described above with respect to the FIGS. 1-2 have been designated by corresponding reference numerals increased by one hundred, two hundred, three hundred and four hundred, respectively. The embodiments and elements thereof for FIGS. 3-6 are designed for use in the same manner as the embodiment of FIGS. 1-2, unless otherwise indicated.

FIG. 3 shows the belt freezer apparatus of FIG. 1 in a dual chamber arrangement shown generally at 110. This apparatus 110 may be used as a cryogenic production rate booster for conventional dual belt flat product freezers. As production demands of hamburger patty manufacturers increase (there are requirements that now need to produce 8000 lbs/hr), known mechanical freezing systems cannot meet the new requirements. This freezer embodiment, as with the other embodiments of the invention, provides a small footprint, low cost, add-on solution.

The housing 12,112 of the freezer apparatus 10,110 may be provided with one or a plurality of doors 30,130 as shown in FIGS. 1-3. The doors 30,130 may be mechanically fitted to the housing 12,112 to provide access to the chamber 14,114 and conveyor belt(s) 16,116 therein. At least one of the doors 30,130 and the housing 12,112 would have a gasket or seal where the door removably contacts the housing. A floor 19,119 of the housing 12,112 may be pitched at an angle downward toward the doors 30,130 for accumulated debris and liquid to flow toward the doors for removal, instead of accumulating or pooling in the chamber 14,114. The pitch or grade may be for example 3° off the horizontal of the floor of the chamber 14,114.

Owing to the perspective of FIGS. 1-6, only one of the blowers 28 is viewable in the FIGS. However, a plurality of the blowers 28 may be arranged along the housing 12 for communication with the chamber 14,114, etc.

Embodiments in FIGS. 4-6 may differ from the embodiments shown in FIGS. 1-3 in that the embodiments of FIGS. 4-6 include airflow baffles and conveyor belts constructed and arranged to be exposed to the airflow in a somewhat different manner than the embodiments shown in FIGS. 1-3. In addition, and referring to the embodiment of FIG. 4, there is a secondary airflow baffle or arcuate member 21 which obviates the need for a side wall of the freezer enclosure to be provided with an arcuate inner surface (such as shown at 24 in FIG. 1 for example).

Referring to FIG. 4, a freezer apparatus shown generally at 210 includes an interior chamber 214 in which an airflow baffle 220 is disposed for coaction with an arcuate air guide baffle 21. The baffle 21 may be constructed of solid or nonporous material and formed as an arcuate member as shown in FIG. 4. The baffle 21 extends along an entire length of the chamber 214. The airflow baffle 220 is solid in construction and includes a proximal end which extends from the blower 228 to a position in the chamber 214 away from the blower toward an opposing side wall 230 which can function as a door to the chamber 214, or to arcuate member 21 discussed below. Disposed below baffle 220 is the secondary air guide baffle 21 which extends from an interior wall 29 near the blower 228 in the housing 212 to an opposed side of the housing proximate the door 230. The secondary baffle 21 is solid in construction, and is bent or curved as the baffle 21 approaches the door 230, but does not touch the door. An end of the secondary air guide baffle 21 arches or is turned upward in spaced relation from the door 230 to contact a ceiling 27 or upper interior side wall of the housing 212. As shown in FIG. 4, the secondary baffle 21 is spaced from a bottom 25 of the enclosure 212.

Disposed between the airflow baffle 220 and the secondary air guide baffle 21 is a conveyor belt 216 for transporting product 218 in the apparatus 210. Another conveyor belt 15 is disposed closer to the bottom 25 of the chamber 214, the belt 15 being disposed beneath the secondary air guide baffle 21. Alternatively, the belts 15 and 216 are the same, as FIG. 4 shows a cross-section of a single belt, wherein an upper portion 216 of such belt is disposed between the airflow baffle 220 and the airguide baffle 21; while a lower portion of such belt 15 is disposed beneath the air-guide baffle 21.

Airflow 223 of the embodiment of FIG. 4 is moved from the blower 228 through a first region “X”, which is the region also above the secondary air guide baffle 21. The airflow 223 moves across the region X where it is charged with a cryogen above the airflow baffle 220 and as it approaches the distal end of the airflow baffle 220 it encounters the secondary air guide baffle 21 and is turned or deflected downward to a lower area of the region X for being moved in a transverse direction across the food product 218 being transported on the conveyor belt 216. The airflow 223 is turned by the arcuate structure of the air guide baffle 21 to be directed between the airflow baffle 220 and the airguide baffle 21 to contact the product 218 on the conveyor belt 216. Thereafter the airflow is drawn back up into an inlet 226 of the blower 228 for subsequent processing and cooling. Cryogen nozzles 222 replenish the cryogen supply for the airflow 223. The number of the cryogen nozzles 222 is by way of example only and depending upon the application and the product to be frozen, such will dictate the number of nozzles 222 needed for the embodiment The nozzles 222 are connected to a remote source of cryogen fluid (not shown).

The lower conveyor belt 15 is actually a return portion of the conveyor belt 216, i.e. owing to the perspective of the drawing figure, the conveyor belt 216 is transporting the product 218 into or out of the Figure and so what we are viewing is the product 218 being conveyed by the conveyor 216 through the region X after which the product 218 is removed from the freezer apparatus 210 and the conveyor belt is functioning as a continuous loop so that we see the bottom portion 15 of the conveyor belt 216 returning to accept another load of the product 218.

In the embodiment of FIG. 4, as with the embodiments shown in FIGS. 1-3, 5 and 6, the airflow 223 is transverse to the direction of movement of the conveyor belt 218 so that the food product 218 is exposed for its entire period of time in the chamber 214 to the chilling airflow 223 as the food product 218 is transported through the freezer apparatus 210. The solid construction of both the airflow baffle 220 and the secondary airguide baffle 21 segregates the airflow so that same is subjected to the food product 218 only in the region “Y”, not wastefully in the space beneath the secondary airguide baffle 21 at the portion 15 of the conveyor.

Referring to FIG. 5, another embodiment of a freezer apparatus is shown generally at 320. In this freezer embodiment 310, the airflow baffle 320 extends from the blower 328 toward but spaced apart from a door 330 of the apparatus 310. A conveyor 316 for transporting the product 318 to be frozen is disposed in a chamber 314 of the housing 312 such that a lower portion 15 of the conveyor belt 316 is spaced apart from a bottom of the housing 312. The airflow 323 emitted from the blower 328 proceeds along the space “X” between the conveyor belt 316 and its bottom portion 15, the airflow 323 prevented from contacting the conveyor belt 316 due to the solid construction of the airflow baffle 320. As the airflow 323 reaches a distal end of the chamber 314 proximate the door 330, it is turned or guided in a rearward and an opposite direction by the interior arcuate wall of the door 330 to enter the region “Y” where the airflow 323 is subjected to jet sprays from cryogen nozzles 322 disposed in a roof of the housing 312. The airflow 323 is in effect “charged” with the freezing cryogen for contacting the food product 318 on the conveyor belt 316 in region Y. Due to the solid construction of the airflow baffle 320, the airflow 323 charged with the cryogen is prevented from drifting downward into the region “X”, but is instead further guided back to the blower inlet 326 where it is drawn in and recirculated again to the region “X” between the conveyor belt portions 316,15.

FIG. 6 is another embodiment of the freezer apparatus shown generally at 410. A housing 412 of the apparatus 410 is constructed with at least one and preferably a plurality of the blowers 428 (only one of which is shown due to the perspective of the drawing figure). The housing 412 is constructed at opposed sides of the blower(s) 428 with elements similar to that shown in the embodiment of FIG. 5. That is, the apparatus 410 of FIG. 6 includes construction of the embodiment of FIG. 5 replicated at an opposed side of the blower 428. It can be seen from FIG. 6 that the airflow 423 and coaction of elements of FIG. 6 operate similar to that which is disclosed and described with respect to the embodiment of FIG. 5. FIG. 6 therefore provides for a larger volume of the food product 418 to be frozen and/or to be frozen in a lesser amount of time. The embodiment shown in FIG. 6 serves a purpose similar to the embodiment shown in FIG. 3. That is, the embodiment of FIG. 6 provides a cryogenic production rate booster for conventional dual belt flat product freezers that require larger production demands.

It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as described and claimed herein. It should be understood that the embodiments described above are not only in the alternative, but may be combined. 

1. An apparatus for processing a food product with a cooling gas, comprising: a housing; a chamber disposed in the housing; a blower in communication with the chamber for circulating the cooling gas in the chamber; a baffle disposed in the chamber for dividing the chamber into a first region of the chamber for exposing the food product to the cooling gas and a second region of the chamber in which the cooling gas is moved by the blower for recirculation to the first region of the chamber; an arcuate member disposed in the chamber in spaced relationship with the baffle for providing a flow path between the first and second regions, the arcuate member coacting with the baffle to guide the cooling gas into the flow path; and conveyor means disposed for movement through at least one of the first and second regions for supporting and delivering the food product through the cooling gas.
 2. The apparatus according to claim 1, wherein the arcuate member comprises an interior surface in the chamber of the housing.
 3. The apparatus according to claim 2, wherein the interior surface comprises a curved portion of a sidewall of the housing, the curved portion proximate the flow path.
 4. The apparatus according to claim 1, wherein the arcuate member comprises a longitudinal member extending from an area of the first region into the second region, the longitudinal member including a curved portion proximate the flow path.
 5. The apparatus according to claim 1, wherein the baffle is constructed of nonporous material.
 6. The apparatus according to claim 4, wherein the longitudinal member is constructed of nonporous material.
 7. The apparatus according to claim 1, further comprising a cryogen charging assembly in communication with at least one of the first and second regions of the chamber for providing cryogen fluid to the cooling gas.
 8. The apparatus according to claim 7, wherein the cryogen charging assembly comprises at least one nozzle disposed in the chamber.
 9. The apparatus according to claim 7, wherein the cryogen fluid is selected from cold gas, carbon dioxide, nitrogen and mixtures thereof.
 10. The apparatus according to claim 3, wherein the sidewall comprises a door for the housing.
 11. The apparatus according to claim 1, wherein the housing further comprises a floor disposed in the chamber, the floor constructed on a grade off the horizontal and tilted downward within the chamber toward the arcuate member.
 12. The apparatus according to claim 1, wherein the first region and the flow path extend across an entire surface of the conveyor means upon which the food product is supported, for guiding the cooling gas in a direction across the food product perpendicular to movement of the food product in the chamber.
 13. The apparatus according to claim 1, wherein the baffle is disposed in the chamber having a proximate end positioned at the blower and a distal end extending in the chamber toward the arcuate member.
 14. The apparatus according to claim 1, wherein the baffle is adapted for movement within the chamber to accommodate height of the food product on the conveyor means in the chamber.
 15. The apparatus according to claim 1, wherein the blower is disposed in the chamber.
 16. A method of applying a cooling gas to a food product, comprising: conveying a food product along a first path to be cooled in a chamber for cooling; circulating a cooling gas in the cooling chamber along a second path perpendicular to an entire length of the first path; and exposing the food product to the cooling gas moving along the second path for an entire length of the first path in the cooling chamber.
 17. The method according to claim 16, further comprising charging the cooling gas with a cryogenic fluid at a select location in the cooling chamber during the circulating of the cooling gas.
 18. The method according to claim 17, wherein the cryogenic fluid is selected from cold gas, carbon dioxide, nitrogen and combination thereof.
 19. The method according to claim 16, further comprising dividing the cooling chamber into a first region wherein the food product is conveyed along the first path for exposure to the cooling gas circulating along a second path, and a second region wherein the cooling gas is recirculated in the chamber.
 20. The method according to claim 19, further comprising adjusting a height of the first region to accommodate a height of the food product. 